Promoter methylation-associated loss of ID4 expression is a marker of tumour recurrence in human breast cancer

Background Inhibitor of DNA binding/Inhibitor of differentiation 4 (ID4) is a critical factor for cell proliferation and differentiation in normal vertebrate development. ID4 has regulative functions for differentiation and growth of the developing brain. The role of ID1, ID2 and ID3 are expected to be oncogenic due to their overexpression in pancreatic cancer and colorectal adenocarcinomas, respectively. Aside from these findings, loss of ID3 expression was demonstrated in ovarian cancer. The aim of the present study was to reveal the factual role of ID4in carcinogenesis in more detail, since its role for the pathogenesis of human breast cancer has been discussed controversially, assigning both oncogenic and tumour suppressive functions.